The Effect of Liver Extract in Cultures of Megaloblastic Bone Marrow

N-terminal (atrial natriuretic factor (ANF) 1-98) and C-terminal (ANF 99-126) fragments of proatrial natriuretic factor (NTA and CTA, respectively) were determined in plasma of healthy subjects adopting different postures and in patients with cirrhosis. Seven healthy subjects were investigated while seated and 30 min after assuming a horizontal position. NTA plasma concentrations increased in subjects in the horizontal position (from 734±250 (SE) fmol/ml to 9021227 fmol/ml; p<0.05). In contrast, CTA plasma concentrations remained unchanged (9.2+1.3 fmol/ml vs 8.9±1.6 fmol/ml). In 10 patients with cirrhosis of the liver, NTA concentrations were markedly (p<0.001) elevated compared to 11 healthy subjects (2334±291 fmol/ml vs 743±155 fmol/ml). However, there was no difference of CTA plasma levels between cirrhotic patients and healthy subjects (8.7±1.3 fmol/ml vs 8.2±0.9 fmol/ml). These data demonstrate changes of the plasma concentration of the N-terminal fragment of proatrial natriuretic factor by posture and in liver disease, in contrast to unchanged levels of the C-terminal fragment.     

Clearance of atrial natriuretic factor by lung, liver, and kidney in human subjects and the dog.

We determined human and canine plasma clearance of atrial natriuretic factor (ANF) by lung, liver, and kidney from arteriovenous differences in plasma ANF and measured organ plasma flow. Human subjects had lower plasma ANF concentrations in the pulmonary vein or the pulmonary capillary wedge position when compared with the pulmonary artery, and both sites yielded pulmonary ANF extraction ratios of 24%. Canine lung ANF extraction was 19 +/- 3% and pulmonary ANF clearance was 328 +/- 78 ml/min per m2 vs. 357 +/- 53 ml/min per m2 in man. Hepatic plasma ANF clearance was 216 +/- 26 ml/min with an extraction ratio of 30 +/- 3% in humans and 199 +/- 89 ml/min and 36 +/- 6% in the dog. Renal plasma ANF clearance in human subjects was 78 +/- 12 ml/min per kidney and correlated well with each kidney's creatinine clearance (r = 0.58, P less than 0.05). The mean renal ANF extraction ratio was 35 +/- 4% in human subjects and 42 +/- 6% in the dog. These data quantitate the specific organ ANF clearances by lung, liver, and kidney in human subjects and in dogs and provide a rationale for elevated plasma ANF levels in cirrhosis, renal failure, and diseases accompanied by reduced perfusion of these organs. These findings support the conclusion that plasma ANF concentrations are dependent upon both the stimuli for ANF secretion as well as the specific organ clearances of ANF.     

Relationship of increased plasma atrial natriuretic factor and renal sodium handling during immersion-induced central hypervolemia in normal humans.

Although maneuvers augmenting atrial volume and/or stretch also augment plasma levels of atrial natriuretic factor (ANF), the role of ANF in modulating renal sodium and water handling has not been defined. Water immersion to the neck (NI) was employed to assess the ANF response to acute volume expansion in 13 seated sodium-replete normal subjects. ANF increased promptly and markedly from 7.8 +/- 1.8 to 19.4 +/- 3.8 fmol/ml, then declined to 6.3 +/- 1.4 fmol/ml after 60 min recovery. Concomitantly, NI increased urine flow rate (V) (2.0 +/- 0.6 to 7.0 +/- 0.9 ml/min; P less than 0.001) and sodium excretion (UNaV) (92 +/- 12 to 191 +/- 15 mu eq/min; P less than 0.001), and decreased PRA (-66 +/- 3%) and plasma aldosterone (-57 +/- 6%). Increases of plasma ANF ranged from less than 20% to over 12-fold. Similarly, the natriuretic response to NI varied markedly from none to 500%. There was a strong correlation between peak ANF and peak UNaV (r = 0.67; P less than 0.025), but none between peak V and peak plasma ANF (r = -0.10; P greater than 0.5). These findings suggest that an increase in plasma ANF contributes to the natriuretic response to NI, implying a physiological role for ANF in modulating volume homeostasis in humans.     

Atrial natriuretic factor in human blood.

To determine whether atrial natriuretic factor (ANF) is a circulating hormone in men, a radioimmunoassay suitable for the estimation of ANF in human plasma was developed and the nature of plasma ANF was characterized. Plasma ANF was extracted before radioimmunoassay by affinity chromatography on a column of ANF antibody-coupled agarose. When plasma ANF extract was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with the radioimmunoassay of the eluted gel slices for ANF, almost all of the ANF activities ran in the 3,000-mol-wt area, while three peaks of ANF were observed in human atrial tissue extract, molecular weights of which corresponded to 14,000, 6,000, and 3,000, respectively. Reversed-phase high performance liquid chromatography of atrial tissue extract resolved multiple forms of ANF. In contrast, one major peak was observed in human plasma extract, and its retention time coincided with that of synthetic human alpha-atrial natriuretic polypeptide. When 500 ml of 0.9% saline was infused into six healthy subjects over 45 min, plasma levels of ANF were unequivocally elevated. The mean plasma ANF concentrations rose from the baseline (23.0 +/- 2.5 pg/ml, mean +/- SEM, n = 6) to the peak (41.8 +/- 4.9 pg/ml, mean +/- SEM) at 75 min postinfusion. No significant change in plasma ANF, on the other hand, was found in the control group. These results suggest that ANF is a circulating hormone in men and is secreted in response to isotonic volume expansion.     

Role of atrial natriuretic factor, cyclic GMP and the renin–aldosterone system in acute volume regulation of healthy human subjects

The role of the atrial natriuretic factor (ANF), its second messenger cyclic guanosine monophosphate (cGMP), and the counteracting renin-aldosterone system in acute volume regulation was investigated in 25 healthy human subjects. Central volume stimulation by 1-h head-out water immersion (WI) into a thermoneutral water-bath increased plasma levels of ANF (mean +/- SEM) from 6.0 +/- 0.6 to 13.6 +/- 2.6 fmol ml-1. This was paralleled by a rise of plasma cGMP levels from 1.9 +/- 0.2 to 2.8 +/- 0.4 pmol ml-1, and an increase of urinary cGMP excretion from 340 +/- 64 to 692 +/- 103 pmol min-1. Water immersion reduced plasma aldosterone concentration (PAC) from 13.0 +/- 1.7 to 6.5 +/- 0.8 ng 100 ml-1 and plasma renin activity (PRA) from 5.3 +/- 0.9 to 2.4 +/- 0.3 ng AI ml-1 h-1. Volume stimulation markedly increased diuresis and natriuresis. Whereas the plasma cGMP increase correlated with plasma ANF stimulation, neither ANF nor PRA or PAC correlated with basal or stimulated renal parameters. Water immersion-induced changes in natriuresis and urinary cGMP excretion were correlated. These data suggest a role of ANF and cGMP in acute volume regulation of healthy human subjects.     

Effects of hyperglycaemia on kidney function, atrial natriuretic factor and plasma renin in patients with insulin-dependent diabetes mellitus.

In normoalbuminuric patients with insulin-dependent diabetes mellitus, plasma atrial natriuretic factor (ANF), cyclic GMP and active renin and the renal clearances of [99Tcm]-diethylenetriaminepentaacetic acid (DTPA) lithium and sodium were studied on a hyperglycaemia day and a euglycaemia day. Baseline euglycaemia was achieved by an overnight variable insulin infusion, which during study days was fixed at the rate necessary to maintain euglycaemia in the morning. After a baseline euglycaemic clearance period of 90 min, measurements were repeated in a new 90-min period beginning 150 min later. On the hyperglycaemia day i.v. infusion of 20% glucose was started at the end of the euglycaemic baseline period, increasing blood glucose (5.3 +/- 1.3 vs 12.1 +/- 1.2 mmol l-1, p less than 0.01). On the euglycaemia day blood glucose declined (5.1 +/- 1.0 vs 4.2 +/- 1.0 mmol l-1, p less than 0.02). Glomerular filtration rate (GFR) was unchanged by acute hyperglycaemia (127 +/- 16 vs 129 +/- 24 ml min-1, NS), but nearly normalized during maintained euglycaemia on the euglycaemia day (124 +/- 17 vs 105 +/- 16 ml min-1, p less than 0.01). When comparing the hyperglycaemic study period with the similarly timed period on the euglycaemia day, GFR was elevated by hyperglycaemia (129 +/- 24 vs 105 +/- 16 ml min-1, p less than 0.01), while the renal clearances of lithium and sodium were similar. Consequently, the calculated absolute proximal reabsorption rate of sodium and water was elevated during hyperglycaemia. Hyperglycaemia reduced the slight decline in plasma concentrations of ANF and cyclic GMP observed on the euglycaemia day. Active renin, glucagon and plasma osmolality were unchanged. In conclusion, marked changes in glomerular filtration rate are induced by changes in blood glucose concentration, but the effect is delayed and thus not directly related to renal tubular transport of glucose. Hyperglycaemia does not affect renal clearances of lithium and sodium, while proximal tubular reabsorption is markedly stimulated. These changes are not related to changes in ANF, renin, glucagon or plasma osmolality.     

Plasma levels of immunoreactive atrial natriuretic factor in healthy subjects and in patients with edema.

Atrial natriuretic factor (ANF), a recently sequenced cardiac peptide, has been shown to have potent natriuretic, diuretic, and vasodilating effects in several species. We have developed a radioimmunoassay to measure the levels of immunoreactive ANF in human plasma. Plasma levels of ANF in healthy volunteers on a low sodium diet were 9.8 +/- 1.4 pmol/liter and increased to 21.9 +/- 3.0 on a high sodium diet. The levels of atrial natriuretic factor correlated directly with urinary sodium and inversely with plasma renin activity and plasma aldosterone levels. Patients with marked edema due to congestive heart failure had plasma levels of atrial natriuretic factor five times higher than normal (P less than 0.05), whereas patients with cirrhosis and edema had levels that were not different from normal. These results suggest that atrial natriuretic factor plays an important role in the adaptation to increased sodium intake.     

Elevated fasting cholecystokinin levels in pancreatic exocrine impairment: evidence to support feedback regulation

Previous studies have suggested that intraduodenal protease suppression of pancreatic exocrine secretion may be mediated through cholecystokinin (CCK) release. Our study compares basal plasma immunoreactive CCK concentrations in normal human subjects with those obtained in patients with chronic pancreatitis. Fasting plasma samples were collected from 18 normal subjects and from 18 patients with chronic pancreatitis. Eight patients had mild to moderate pancreatic exocrine impairment, and 10 had severe exocrine insufficiency. Venous plasma immunoreactive CCK concentrations were measured with two distinct peptide region-specific antibodies. Basal plasma CCK concentration in controls was 14.3 +/- 1.3 fmol/ml (mean +/- SEM), a value significantly less than that obtained in all patients with chronic pancreatitis, 30.1 +/- 4.0 fmol/ml (p less than 0.001). Patients with mild to moderate impairment had a fasting plasma CCK concentration of 32.8 +/- 7.9 fmol/ml (vs. control p less than 0.01), and those with severe disease 27.9 +/- 3.6 fmol/ml (vs. control p less than 0.001). In five patients with mild to moderate impairment of exocrine function and pancreatic extract-responsive abdominal pain, there was a 39 +/- 11% decrease in basal CCK levels during extract therapy (p less than 0.05). Results of this study indicate that pancreatic exocrine impairment is associated with elevated basal CCK levels, which may reflect a failure to provide feedback downmodulation of CCK release.     

Atrial natriuretic factor: comparability of venous and arterial plasma measurements in man at rest and during exercise

1. Simultaneously obtained arterial and venous plasma atrial natriuretic factor (ANF) concentrations were compared at supine rest and during graded dynamic leg exercise in 10 healthy male subjects (aged 33-51 years). 2. Arterial ANF concentrations ranged between 12 and 179 pg/ml and venous concentrations between 9 and 177 pg/ml. 3. A positive correlation between arterial and venous concentrations was found (r = 0.984). 4. Arterial ANF concentrations were higher than venous concentrations in all pairs of samples (n = 31), but the difference was small and changed little with exercise: the mean difference was 5 pg/ml at rest, 12 pg/ml during submaximal exercise and 6 pg/ml during maximal exercise. 5. The extraction ratios for ANF varied greatly, but were in general lower (P less than 0.05) during maximal exercise (median 0.07, range 0.01-0.32) than at rest (median 0.22, range 0.05-0.33). 6. It was concluded that the plasma ANF concentration in a peripheral arm vein is a good indicator of the systemic peptide concentration at rest as well as during dynamic leg exercise.     

Plasma bradykinin levels in human chronic congestive heart failure

Induction of congestive heart failure by high-frequency pacing has been reported to increase plasma levels of immunoreactive kinins in dogs. In the present study, we evaluated plasma bradykinin levels in human heart failure. Utilizing a recently developed method, we specifically measured plasma levels of bradykinin-(1-9) nonapeptide in 21 patients with chronic congestive heart failure [New York Heart Association (NYHA) stages III and IV). At the same time, we measured plasma atrial natriuretic peptide levels and plasma renin activity, and, as a marker of inflammation, plasma levels of tumour necrosis factor. In addition, 18 healthy subjects matched for gender and age served as normal controls. Plasma bradykinin concentrations were not higher in patients with chronic congestive heart failure (median 2.1 fmol/ml) than in healthy subjects (2.6 fmol/ml). In contrast, plasma atrial natriuretic peptide levels were clearly higher (patients, 63 fmol/ml; controls, 24 fmol/ml; P<0.0001), despite diuretic treatment and in the presence of high plasma renin activity (patients, 13.0 ng x h(-1) x ml(-1); controls, 0.3 ng x h(-1) x ml(-1); P<0.0001). Tumour necrosis factor was elevated in heart failure patients in NYHA class IV only (27 pg/ml, compared with 21 pg/ml in controls; P=0.013). Bradykinin, atrial natriuretic peptide and plasma renin activity levels were not correlated with the severity of the disease, as assessed by NYHA classification. These results indicate that a rather selective cytokine activation, without concomitant stimulation of the kallikrein-kinin system, occurs in human chronic congestive heart failure.     

Atrial natriuretic factor in normal subjects and heart failure patients. Plasma levels and renal, hormonal, and hemodynamic responses to peptide infusion.

We investigated atrial natriuretic factor (ANF) in humans, measuring plasma immunoreactive (ir) ANF (in femtomoles per milliliter), and renal, hormonal, and hemodynamic responses to ANF infusion, in normal subjects (NL) and congestive heart failure patients (CHF). Plasma irANF was 11 +/- 0.9 fmol/ml in NL and 71 +/- 9.9 in CHF (P less than 0.01); the latter with twofold right ventricular increment (P less than 0.05). In NL, ANF infusion of 0.10 microgram/kg per min (40 pmol/kg per min) induced increases (P less than 0.05) of absolute (from 160 +/- 23 to 725 +/- 198 mueq/min) and fractional (1-4%) sodium excretion, urine flow rate (from 10 +/- 1.6 to 20 +/- 2.6 ml/min), osmolar (from 3.2 +/- 0.6 to 6.8 +/- 1.2 ml/min) and free water (from 6.8 +/- 1.6 to 13.6 +/- 1.6 ml/min) clearances, and filtration fraction (from 20 +/- 1 to 26 +/- 2%). Plasma renin and aldosterone decreased 33% and 40%, respectively (P less than 0.01). Systolic blood pressure fell (from 112 +/- 3 to 104 +/- 5 mmHg, P less than 0.05) in seated NL; but in supine NL, the only hemodynamic response was decreased pulmonary wedge pressure (from 11 +/- 1 to 7 +/- 1 mmHg, P less than 0.05). In CHF, ANF induced changes in aldosterone and pulmonary wedge pressure, cardiac index, and systemic vascular resistance (all P less than 0.05); however, responses of renin and renal excretion were attenuated. ANF infusion increased hematocrit and serum protein concentration by 5-7% in NL (P less than 0.05) but not in CHF.     

Solid-phase double-antibody radio-immunoassay for atrial natriuretic factor

A solid-phase radio-immunoassay for the determination of atrial natriuretic factor (ANF) in human plasma is described. Iodination of alpha hANF was carried out with the iodogen method. Purification of radio-iodinated alpha hANF was performed by chromatography on disposable columns of DEAE-Sephadex A-25. Studies of immunoreactivity and the elution pattern on HPLC showed perfect stability of the labelled compounds. The tracer was usable for 28 weeks after preparation, and the batch-to-batch variation in the quality of the tracer was satisfactory. Immunoreactive ANF was extracted from human plasma with Sep-Pak C18 cartridges. Recovery of alpha hANF added to whole blood was 85 +/- 12% (mean +/- SD, n = 12). The sensitivity of the radio-immunoassay was 1.6 pg/tube, equivalent to 1 pg/ml plasma when assaying the extract from 4 ml plasma. Mean plasma ANF values in normal subjects in the supine position was 23 +/- 12 pg/ml (mean +/- SD, n = 21).     

Association between increased atrial natriuretic peptide and reduced cisplatin nephrotoxicity in rats.

Plasma atrial natriuretic peptide (ANP) concentrations were monitored in two experimental models of protection from cisplatin nephrotoxicity. Sprague-Dawley rats made diabetic with streptozotocin (65 mg/kg) were protected from cisplatin-induced nephrotoxicity when compared to control rats as indicated by reduced plasma creatinine (0.49 +/- 0.02 vs. 0.9 +/- 0.06 mg/dl; P less than .001) and blood urea nitrogen concentrations (18.51 +/- 1.4 vs. 43.08 +/- 2.1 mg/dl; P less than .001). Plasma ANP was also increased with experimental diabetes (76.5 +/- 8.98 fmol/ml) vs. normoglycemic controls (43.8 +/- 8.9 fmol/ml; P less than .02). When diabetic rats were treated with insulin, the renal protection observed with the diabetic state was reversed (creatinine, 0.70 +/- .05 mg/dl); plasma ANP concentrations were also reduced (52.2 +/- 15.2 fmol/ml). Renal platinum concentrations were significantly lower in the diabetic group and the reversal of diabetic-induced renal protection with insulin was associated with increased renal platinum concentrations. In rats given a single i.p. dose of cisplatin (5 mg/kg), a reduction in cisplatin-induced nephrotoxicity was observed when 5% NaCl was the vehicle of choice compared to that seen in rats given the same dose of drug in 0.9% saline (creatinine, 0.43 +/- 0.07 with 5% NaCl vs. 0.63 +/- 0.03 with 0.09% NaCl). NaCl (5%) administration also resulted in increased plasma ANP concentrations when compared to rats receiving equivalent volumes of 0.9% NaCl (88.4 +/- 6.2 vs. 50.5 +/- 5.6 fmol/ml, respectively). These data suggest that increased endogenous ANP may be a mechanism of renal protection common to both experimental diabetes and hypertonic saline administration. Chronically increased ANP may prevent renal accumulation of platinum in the kidney.     

SCH 39370, a neutral metalloendopeptidase inhibitor, potentiates biological responses to atrial natriuretic factor and lowers blood pressure in desoxycorticosterone acetate-sodium hypertensive rats

SCH 39370 (N-[N-[1-(S)-carboxyl-3-phenylpropyl]-(S)-phenyl-alanyl]-(S)-isoserin e) is a potent and specific inhibitor of neutral metalloendopeptidase (NEP) from rabbit kidney (IC50 = 11.2 +/- 1.9 nM) and is devoid of angiotensin-converting enzyme inhibitory activity at 1 microM. We evaluated the effect of NEP inhibition with SCH 39370 on the inactivation of atrial natriuretic factor (ANF) and on cardiovascular function in rats. SCH 39370 effectively prevented in vitro degradation of ANF (99-126) by a purified rabbit kidney NEP. SCH 39370 (30 mg/kg s.c) significantly delayed the disappearance of immunoreactive (ir) ANF from plasma in rats after an i.v. infusion of ANF (1 microgram/kg/min for 30 min): the plasma ir ANF level at 15 min postinfusion was 1.5 +/- 0.3 ng/ml vs. 0.3 +/- 0.04 ng/ml in the control. SCH 39370 also delayed the disappearance of ir ANF after infusion of the peptide (0.1 microgram/kg/min for 30 min) which increased plasma levels to those observed during volume expansion. This effect was accentuated markedly in rats with bilateral nephrectomy. The hypotensive response to injection of ANF (30 micrograms/kg i.v.) in spontaneously hypertensive rats (-38 +/- 6 mm Hg vs. -13 +/- 2 mm Hg in the control) and the diuretic and natriuretic responses to ANF in normal rats were potentiated by SCH 39370 (30 mg/kg s.c.), respectively. The results suggest that NEP can play a role in ANF disposition in vivo and that potentiation of the biological activities of high doses of ANF by SCH 39370 may be consequent to its inhibitory effect on ANF degradation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic effects of atrial natriuretic factor in young and elderly subjects

Because levels of plasma atrial natriuretic factor (ANF) increase with advancing age, a diminished hemodynamic responsiveness to ANF in the elderly has been hypothesized in the literature. Therefore hemodynamic effects after two infusion rates (0.25 and 2.0 micrograms/min) of atrial natriuretic factor (99-126) were investigated in young (n = 8) and elderly (n = 9) volunteers in a double-blind, randomized, and placebo-controlled protocol. After low-rate infusion, ANF concentrations increased to the upper normal range, and only minor effects were observed. In contrast, high-rate infusion resulted in a decrease in blood pressure and forearm vascular resistance, whereas an increase in heart rate was observed in both groups. Between young and elderly subjects, a significant difference was observed in the ANF-induced decrease in systolic blood pressure (mean +/- SD, -4% +/- 4% versus -12% +/- 7%, p less than 0.05) and mean arterial pressure (-6% +/- 5% versus -11% +/- 4%, p less than 0.05) during the high rate infusion. When compared with the concentrations of the young subjects, the ANF concentrations reached at both ANF dosages were higher in the elderly subjects; this was the result of a diminished ANF clearance in the elderly subjects. After correction of the changes of systolic blood pressure and mean arterial pressure for the higher ANF levels reached within this elderly group, no difference between young and elderly subjects remained. We conclude that a diminished cardiovascular responsiveness to ANF with advancing age could not be demonstrated. In contrast, the high-rate infusion of ANF induced an increased hemodynamic response in the elderly subjects, but this seems to be the result of the higher ANF levels reached within this group.     

Physiological effects of synthetic atrial natriuretic factor in normal conscious dogs

The objective of this study was to examine the integrative physiologic effects of atrial natriuretic factor (ANF). Synthetic 99-126 ANF was administered to 6 normal conscious dogs as two consecutive infusions (0.02 and 0.1 microgram/kg/min respectively) each over 30 min: each infusion was preceded by a priming dose of 1 microgram/kg. With the first infusion, mean arterial pressure declined from 113 +/- 2 to 103 +/- 4 mmHg, pulmonary capillary wedge pressure declined from 9.6 +/- 0.5 to 7.2 +/- 0.7 mmHg and right atrial pressure declined from 9.8 +/- 0.4 to 8.0 +/- 0.7 mmHg (all p less than 0.05). No change in heart rate was seen. Despite very high plasma ANF concentrations, no further decline in arterial or central filling pressures were seen in the second infusion. In contrast, cardiac output declined progressively from 3.8 +/- 0.2 to 2.8 +/- 0.21/min (p less than 0.01) by the end of second infusion. Plasma renin activity declined from 2.2 +/- 0.7 to 0.9 +/- 0.3 ng/ml/hr (p less than 0.05) while plasma norepinephrine remained unchanged. Urine output and sodium excretion increased in a dose dependent manner. The diverse time course of the hemodynamic, renal and neuroendocrine effects suggests these effects of ANF are mediated by different mechanisms. Furthermore, the failure of heart rate and plasma norepinephrine to increase despite a significant decline in blood pressure and cardiac output suggests ANF may have a depressant effect on the sympathetic nervous system.     

Exercise and posture-related changes of atrial natriuretic factor and cardiac function in diabetes

To study whether the release of atrial natriuretic factor (ANF) was altered in diabetic cardiac autonomic neuropathy (CAN), we determined plasma ANF concentrations during exercise and changes of posture in three groups of age- and sex-matched subjects (9 healthy subjects, 7 diabetic patients with CAN, and 7 diabetic patients without CAN). During exercise, plasma ANF concentrations rose threefold (P less than .001), and this increase was similar in the three groups. However, heart-rate response to exercise was impaired in the two groups of diabetic patients (P less than .004 vs. healthy subjects) but was more severely impaired in patients with CAN (P less than .03 vs. patients without CAN). In healthy subjects and patients without CAN, the increases of ANF during exercise correlated significantly with those of heart rate, systolic blood pressure, and rate-pressure product (P less than .01). In patients with CAN, the correlation was found exclusively with heart rate (P less than .01). An increase of ventricular ejection fraction occurred in all groups (P less than .001) but without showing statistical differences between groups. After 30 min of standing, a similar postural drop of plasma ANF concentrations (P less than .002) was observed in all subjects, reflecting preserved sympathetic control of vessels. In conclusion, exercise induces an increase of plasma ANF in diabetic patients with CAN. This increase, occurring similarly to healthy subjects, indicates that autonomic activation plays a minor role in ANF release during exercise. Impaired heart-rate response to exercise in patients without CAN suggests early damage of autonomic function, undetected by conventional rest tests.     

Pharmacokinetics and protein binding of cefpiramide in patients with alcoholic cirrhosis

The pharmacokinetics of cefpiramide, a new cephalosporin, were investigated after a single 1 gm intravenous injection in 11 patients with alcoholic cirrhosis and compared with those of 11 healthy subjects. In patients with cirrhosis the plasma elimination half-life was three times longer than that in normal subjects. The total plasma clearance was decreased significantly (p less than 0.001): 12.3 +/- 6.5 ml/min in patients and 25.6 +/- 4.6 ml/min in healthy volunteers, respectively. The urinary excretion of unchanged drug (percent of intravenous dose) for patients (69.8% +/- 29.9%) was statistically higher (p less than 0.01) than that for subjects (16.2% +/- 3.9%). The renal elimination became increasingly important with hepatic impairment. Protein binding of cefpiramide was reduced significantly in the group with cirrhosis. The average unbound fraction was 10.4% +/- 9.5% in patients with cirrhosis and 1.9% +/- 0.3% in normal subjects (p less than 0.01). Because the rate of elimination from plasma in patients is slower, the dosage regimen of cefpiramide would probably be modified in cirrhosis.     

Diagnosis of heart failure using urinary natriuretic peptides

In the present study, we assessed the use of urinary natriuretic peptides [N-terminal proatrial natriuretic peptide (N-ANP) and N-terminal pro-brain natriuretic peptide (N-BNP) and C-type natriuretic peptide (CNP)] in the diagnosis of heart failure. Thirty-four consecutive hospitalized heart failure patients (median age, 75.5 years; 14 female) were compared with 82 age- and gender-matched echocardiographically normal controls. All subjects provided plasma and urine specimens. Plasma was assayed for N-BNP, and urine was assayed for N-ANP, N-BNP and CNP. The diagnostic efficiency of peptides was assessed using receiver operating characteristic (ROC) curve analysis. All three urinary natriuretic peptides were significantly elevated in heart failure patients ( P <0.001). Urine N-BNP was correlated with plasma N-BNP ( r (s)=0.53, P <0.0005). Areas under the ROC curves for urinary N-ANP, N-BNP and CNP were 0.86, 0.93 and 0.70 and for plasma N-BNP was 0.96. Correcting urinary peptide levels using urine creatinine produced ROC areas of 0.89, 0.93 and 0.76 respectively. A urine N-BNP level cut-off point of 11.6 fmol/ml had a sensitivity and specificity for heart failure detection of 97% and 78% respectively, with positive and negative predictive values of 64.7 and 98%. In conclusion, although all three natriuretic peptides were elevated in urine in heart failure, urinary N-BNP had diagnostic accuracy comparable with plasma N-BNP. Use of urinary N-BNP for heart failure diagnosis may be suitable for high-throughput screening, especially in subjects reluctant to provide blood samples.     

Effect of dietary sodium on plasma concentration of immunoreactive atrial natriuretic factor in normal humans

Atrial natriuretic factor (ANF) is the name applied to a family of peptides secreted by the atria, endowed with potent natriuretic, vasorelaxant, and aldosterone inhibitory properties, and which has been purified from animal and human atria. A radioimmunoassay of human plasma ANF was developed. Six normal men, aged between 24 and 38, were studied after 4 days on a low-sodium diet (40 mmol per day) and 4 days on a high-sodium diet (300 mmol per day), in random order. Plasma renin activity was suppressed and plasma aldosterone reduced by the high-sodium diet, as expected. Plasma immunoreactive ANF was 47.9 +/- 4.8 pg/ml on the low-sodium diet and rose to 68.1 +/- 5.9 pg/ml on the high-sodium diet (p less than 0.01). These results demonstrate that secretion of ANF by the heart may be modulated by the changes produced by extreme variations in sodium intake.